1. Field of Invention
The invention is directed to expandable casing having an expandable slip for anchoring or securing the expandable casing to a section of upper casing disposed within oil and gas wells.
2. Description of Art
Use of expandable casing to form a “mono-diameter” wellbore within open hole oil or gas wells is known in the art. As is also known in the art, during the formation of mono-diameter wellbores, each completed section of the wellbore is required to be isolated to ensure safe operation during production of the well after completion. By forming a mono-diameter wellbore with the expandable casing as part of the oil or gas well, problems with depth control due to hydraulic effects caused by increasing pressure as the depth of the well is increased are eliminated.
While several methods may be possible for providing zonal isolation, generally, the wellbore is formed in accordance with the prior art by circulating cement around the casing string. During such operations, it is desirable to attach one portion of casing string to another portion of casing string disposed above the first portion prior to pumping cement so that issues with depth control due to hydraulic effects can be avoided. Due to limitations of current hole opening or current reaming technologies, the clearance between the open hole and the expanded liner or casing already disposed within the open hole is insufficient to allow adequate circulation of cement. Thus, the cement needs to be pumped prior to expansion of the expandable casing or liner that is being run-in. Pumping cement after expansion of the expandable casing poses the problem of having a return path for the circulating fluids being displaced by the cement.
This problem is addressed in prior systems by placing windows or holes in the expandable casing that is being run in so that wellbore fluids and cement can circulate through the windows of the expandable casing during cementing of the expandable casing and, thus, into contact with the wellbore. The wellbore fluids and cement flow upward around the liner and through the windows or openings. The cement is used to block the windows as it forms the wellbore. Although, these prior systems result in a wellbore being formed, these prior systems have several shortcomings such as not always adequately blocking the windows, interfering with the expansion of the expandable casing to its set position, and, in some cases, providing an asymmetric casing bore. As is apparent to persons skilled in the art, such shortcomings of the prior systems are not desired.
Accordingly, prior to the development of the present invention, there has been no expandable casing, anchoring system for expandable casing, or method known to the inventors of securing an expandable casing within a section of upper casing disposed in a well that: provides sufficient attachment of the expanding casing to the upper casing; provides complete zonal isolation of the completed section of expandable casing; and provides a flow path for circulating cement during expandable bore construction without the need for the expandable casing to include return ports. Therefore, the art has sought expandable casing, anchoring systems for expandable casing, and methods of securing an expandable casing within a section of upper casing disposed in a well that: provide sufficient attachment of the expanding casing to the upper casing; provide complete zonal isolation of the completed section of expandable casing; and provide a flow path for circulating cement during expandable bore construction without the need for the expandable casing to include return ports.